Hi Brad
I have integrated the payment Module from www.paymex.co.nz - another NZ based credit card payment facility
They provide an excellent reliable service and it takes minutes to set up an account with Paymex
It is very easy to integrate into the E-commerce module (one PaymexPayment.php in the code directory file plus additions to _config.php) and good documentation.

Its a Sub-class of Payment that supports the Paymex Start-Up account as its payment processor
* The Start-Up account allows us to redirect the customer to a secure payment page, and be returned back to Paymex
* upon success.
Original version written by Paymex Limited with support from Jack Pivac (Delphinus) July 2008

If you're still interested in Paymate I have a payment method in development for this and would appreciate any testing.
It's not an overly complicated method and you should be able to use it in production as is, just needs more work on handling the response.

What versions of SS and ecommerce are you running? Same goes for anyone else interested ...

The last stable build of ecommerce (0.5.2) doesn't really work with SS 2.3+ and there are some huge changes between 0.5.2 and the current trunk version (which works better with SS v2.3).

Because of this, I am re-coding the Paymate payment class to work on the current trunk version of ecommerce and am mostly there, just have to get my head around (intelligently) dealing with payment records and receipt emails.

Should have a working version by the end of the week and will post it then.